Cubic Boron Nitride Compact
Active Publication Date: 2011-06-16
ELEMENT SIX TRADE MARKS LTD +1
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Problems solved by technology
High temperatures result in higher “chemical wear” on the cutting tool typically identified as smooth and deep crater formation on the rake face of the tool.
Therefore the main problem in continuous cutting is the deep crater formation as a result of chemical wear thereby reducing the overall strength of the cutting edge.
However, in interrupted cutting operations the main problem is that the tools tend to fail catastrophically by fracturing or chipping due to cyclic impact conditions created by interrupted cutting.
Cyclic mechanical, thermal stresses as well as general wear, (abrasive, adhesive and chemical) during the continuous cutting part of the interrupted cutting process lead to poor tool lives.
Therefore in cutting operations that is a combination of both continuous and interrupted cutting the cutting tool edge tends to fail catastrophically by fracturing and chipping.
The main drawback of these approaches is that the selection of an appropriate bonding aid material for both cBN and the secondary hard phase material is not easily achieved.
This is primarily due to disparate nature of the materials involved.
For example, it is well known in the art that Al and Ti react with cBN to form reaction-bonding ceramic phases, however these metals do not easily produce high strength bonds with the secondary hard phase materials: transition metal carbides, nitrides and carbonitrides.
Likewise, the addition of Ni, Co, Fe—type materials may help bonding between the secondary hard phase particles during sintering, but they do not provide for high strength bonding between cBN particles.
Therefore, prior art low cBN PCBN materials are typically sub-optimally bonded and hence do not perform well in demanding applications such as machining involving heavy interrupted cutting as well as the continuous cutting of hardened steels above HRc40.
Method used
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Improved Performance of Materials of the Invention
[0069]Material A: Reference Material Using ‘Prior Art’ Binder
[0070]Aluminium powder having a particle size of 0.5N0.5)0.8 powder having an average particulate size of ˜5 μm in a 10 weight % ratio. The powder mixture was turbular mixed for 1 hour using stainless steel balls, followed by a pre-reaction heat treatment at 1025° C. for 20 minutes under vacuum. The heat treated powder was subsequently crushed and sieved, followed by attrition milling in hexane using cemented carbide milling media for 4 hours. Thereafter cBN powder having an average grain size of ˜1.2 μm was added to the mixture such that the volume % of the cBN was 60. The mixture was attrition milled for a further hour. The slurry was dried under vacuum and formed into a green compact supported by a cemented carbide substrate. The material was sintered at about 5.5 GPa and at about 1480° C. to produce a polycrystalline cBN compact. The cBN compact thus formed is hereinaft...
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Abstract
A structure with a higher surface area than the area occupied by the structure has a number of pillars (2), the pillars being hollow having an opening (6) extending into the pillar. An intermediate layer is provided on the surface of the pillar and an electrode fills the spaces between the pillars (2). The structure has an enhanced structural stability reducing potential damage especially during manufacture. The structure may be used for capacitors or batteries, for example.
Description
BACKGROUND OF THE INVENTION[0001]This invention relates to cubic boron nitride (cBN) abrasive compacts.[0002]Boron nitride exists typically in three crystalline forms, namely cubic boron nitride (cBN), hexagonal boron nitride (hBN) and wurtzitic cubic boron nitride (wBN). Cubic boron nitride is a hard zinc blend form of boron nitride that has a similar structure to that of diamond. In the cBN structure, the bonds that form between the atoms are strong, mainly covalent tetrahedral bonds. cBN is the second hardest material known to man and hence is a useful industrial material.[0003]cBN has wide commercial application in machining tools and the like. It may be used as an abrasive particle in grinding wheels, cutting tools and the like or bonded to a tool body to form a tool insert using conventional electroplating techniques.[0004]cBN may also be used in bonded form as a cBN compact, also known as PCBN (polycrystalline cBN). cBN compacts comprise sintered masses of cBN particles. When...
Claims
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Login to View More IPC IPC(8): B24D3/06
CPCC22C26/00
InventorCAN, NEDRET
OwnerELEMENT SIX TRADE MARKS LTD